The invention relates generally to protein characterization and identification, and more specifically to an improved method and apparatus for determining the amino acid composition of a portion of a protein.
This and a related process and processing assembly are described in co-pending patent applications entitled "Protein Sequencing and Identification System", Ser. No. 09/274,036, by Vincent Robert Farnsworth and Paul K. Cartier and "Multiple-Sample Cartridge Assembly for Automated Process", Ser. No. 09/274,559, by Vincent Robert Farnsworth, both of which applications are filed on the same day as the present application, and both of which are incorporated herein by reference.
The identification and characterization of proteins is important to correlate particular proteins with disease states and to understand the biological function of proteins. Moreover, with the Human Genome project, there is an increasing need to link newly identified genes with their functional counterparts. Various methods have been described to do this, including, for example, digesting the protein with a specific enzyme such as trypsin and then use a mass spectrometer to analyze the resulting peptide mixture. The protein is identified by comparing the experimental mass profiles, including peptide fragmentation patterns, to the predicted profiles of known proteins stored in the databases.
An alternative approach to identifying a particular protein is two-dimensional polyacrylamide gel electrophoresis. Proteins from the 2D PAGE gel are analyzed, for example by Edman degradation. The Edman degradation process involves the sequential degradation of the N-terminus of a protein or polypeptide which comprises three basic stages: coupling, cleavage, and conversion. See Edman and Begg, "A Protein Sequenator", European Journal of Biochem. 1 (1967) 80-91. The amino acids released from the Edman degradation reactions are then analyzed to determine a partial amino acid sequence, the results of which are correlated with sequence data in the existing DNA and protein databases. Unfortunately, identification of proteins by Edman degradation based sequencing is slow due to the serial nature of the process, which requires each cleaved amino acid to be analyzed prior to proceeding with the next.
These methods are of limited utility, in part because they are slow and expensive. Moreover, only one sample at a time is normally analyzed. What is needed is a way to identify proteins more rapidly and allow multiple samples to be processed in parallel.